Process for manufacturing molded outer covering

ABSTRACT

A process for manufacturing a molded outer covering, comprising the steps of mixing two or more powder resin materials having different colors at a desired mixing ratio to prepare a powder mixture, and then heating the powder mixture in a preheated molded die, so that the powder mixture melts, resulting in a formation of a molded product having a pepper and salt pattern on the outer surface thereof.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a process for manufacturing a moldedouter covering, in particular having an outer surface with a pepper andsalt pattern having different colours.

2. Description of the Related Art

Various interior devices of an automobile, such as an instrument panel,or outer surface of a door trim or an interior ceiling are usuallycovered with an outer covering to provide a comfortable compartment to adriver or passanger.

Known outer coverings for an automobile are usually made of a plasticsheet which is, in turn, made by a calendar machine and which is moldedinto a desired shape in a vacuum forming process or the like.

However, it is only possible to make a plastic outer covering having asingle colour or a few limited colours by the vacuum process of aplastic sheet, and accordingly, molded products obtained often result inlack of variety in colour and pattern. Furthermore, a compartment of anautomatic tends to become dirty or unclean by mud or dust which entersthe compartment when a door of the automobile is opened or closed orwhen a passanger gets in or out of the automobile. In addition to theforegoing, the plastic product tends to become charged with staticelectricity, so that the dust or dirt can be easily applied to the outersurfaces of the plastic product. The applied dust or the dirt isconspicuous, in view of the lack of variety in the colour or pattern ofthe plastic covering, thus resulting in a bad influence on the aestheticimpression of the compartment.

SUMMARY OF THE INVENTION

The primary object of the present invention is to eliminate thedrawbacks mentioned above by providing a process for manufacturing anouter covering suitable for interior devices or interior surfaces of anautomobile, in which a covering having desired patterns and colours canbe easily obtained.

Namely, the object of the present invention is to provide an improvedprocess for manufacturing an outer covering which has a decorative andaesthetic appearance with a pepper and salt pattern having differentcolours and in which dust or dirt even if adhered to the outer surfaceof the covering is not conspicuous.

Another object of the present invention is to provide a process formanufacturing a relatively thin and soft molded product which isagreeable to the touch and which can be advantageously used as an outercovering.

Still another object of the present invention is to provide amanufacturing process in which an outer covering having a desired shapeor profile can be easily and effectively obtained.

In order to achieve the objects mentioned above, according to thepresent invention, there is provided a process for manufacturing anouter covering, comprising the steps of mixing two or more powder resinmaterials having different colours at a desired mixing ratio to make asingle powder mixture, and then heating the powder mixture thus obtainedin a preheated molding die to melt the mixture thereby to obtain amolded outer covering which has a pepper and salt pattern havingdifferent colours on its outer surface.

The invention will be described in detail below with reference to theaccompanying drawings, in which;

FIG. 1 is a schematic view of a powder mixture of which an outercovering of the present invention is made;

FIG. 2 is a sectional view of a molding die in which the powder mixtureis charged; and,

FIG. 3 is an enlarged schematic view of a molded product, i.e. an outercovering manufactured by the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 schematically shows a powder mixture of which an outer coveringcan be made. The powder mixture is made of two or more powder resinmaterials A, B, . . . having different colours which are mixed at adesired mixing ratio. The powder resin materials A, B, etc. can beidentical to each other, for example, both soft polyvinyl chloride (PVC)or its copolymers.

Alternatively, the powder resin materials may be different from orsimilar to each other, for example one is PVC and the other is PVCcopolymer. The powder resin materials have different colours.

The difference in hue and brightness between the colours of the powderresin materials depends on design choice, in accordance with patterns tobe formed on an outer surface of a product.

Preferably, the powder resin materials have different grain sizes.

If the powder resin materials are both PVC powders, fundamentally themelting temperatures of the powders depend on degree of polymerizationof the copolymer or the amount of copolymer, etc. Accordingly, PVCpowders having different melting temperatures can be easily obtained,for example, by selecting the degree of polymerization of the powders.

Preferably, the melting temperatures of PVC powders used in the presentinvention are 160° C. to 220° C. As will be apparent later, the meltingtemperatures of PVC powder used in the present invention are determinedby selecting a mean degree (P) of polymerization thereof. Additives,such as plasticizers, stabilizers, fillers, etc. can be kneaded in PVCpowders, together with stains or colouring agents.

The sizes of grains of PVC powders used in the present invention areapproximately 50μ to 200μ. By using a screening means, PVC powdershaving different grain sizes (diameters) can be easily obtained.

These powder resin materials are mixed at a desired mixing ratio to makea single powder mixture, in accordance with a property of matter orappearance of a product.

The following are six examples of powder mixtures which can beadvantageously used in the present invention. Note, the powder resinmaterials A, B and C in the examples are all PVC's.

EXAMPLE 1

    ______________________________________                                                          A       B                                                   ______________________________________                                        colour              white     light brown                                     mixing ratio (by weight)                                                                            1         1                                             mean degree of polymerization ( -- P)                                                             1030      1030                                            melting temperature  180° C.                                                                          180° C.                                 mean grain size      150μ   150μ                                        ______________________________________                                    

EXAMPLE 2

    ______________________________________                                                         A     B        C                                             ______________________________________                                        colour             red     yellow   brown                                     mixing ratio (by weight)                                                                           2       1        7                                       mean degree of polymerization ( -- P)                                                            1030    1030     1030                                      melting 180° C.                                                                           180° C.                                                                        180° C.                                     mean grain size     150μ                                                                               150μ  150μ                                  ______________________________________                                    

EXAMPLE 3

    ______________________________________                                                         A     B        C                                             ______________________________________                                        colour             red     yellow   brown                                     mixing ratio (by weight)                                                                           2       1       7                                        mean degree of polymerization ( -- P)                                                            1030    1030     780                                       melting temperature                                                                               180° C.                                                                       180° C.                                                                         160° C.                            mean grain size     150μ                                                                              150μ  150μ                                   ______________________________________                                    

EXAMPLE 4

    ______________________________________                                                         A     B        C                                             ______________________________________                                        colour             red     yellow   brown                                     mixing ratio (by weight)                                                                           2       1        7                                       mean degree of polymerization ( -- P)                                                            1300    1300     1030                                      melting temperature                                                                              200° C.                                                                        200° C.                                                                         180° C.                            mean grain size     150μ                                                                               150μ  150μ                                  ______________________________________                                    

EXAMPLE 5

    ______________________________________                                                            A       B                                                 ______________________________________                                        colour                white     brown                                         mixing ratio (by weight)                                                                              1         2                                           mean degree of polymerization ( -- P)                                                               1030      1030                                          melting temperature    180° C.                                                                          180° C.                               mean grain size        80μ    180μ                                      ______________________________________                                    

EXAMPLE 6

    ______________________________________                                                            A       B                                                 ______________________________________                                        colour                white     gray                                          mixing ratio (by weight)                                                                              1         4                                           mean degree of polymerization ( -- P)                                                               1300      1030                                          melting temperature    200° C.                                                                          180° C.                               mean grain size        180μ   80μ                                       ______________________________________                                    

A predetermined amount of the powder mixture as mentioned above isloaded in a molding die 2 which has a cavity 1 of a desired shape, asshown in FIG. 2.

The molding die 2 is preheated at a predetermined temperature (150°˜200°C.), so that the powder mixture loaded in the die 2 can be heated withthe result that the powder mixture melts and the grains of the powderare adhered to each other. An excess of powder is removed from the die.

After that, a further heating of the die 2 takes place for apredetermined time to heat the powder, by means of a heating device 4which will be described hereinafter, resulting in a complete adhesion ofthe grains and also in the formation of a desired thickness of moltenresin layer. If necessary, the die 2 can be rotated or revolved toprovide a uniform adhesion of the grains of the powder.

After that the die 2 is cooled to cure the resin layer, so that a curedouter covering made of a resinous sheet having a desired shape can beobtained.

In the manufacturing process mentioned above, according to the presentinvention, the powder resin materials to be mixed have different coloursand preferably different melting temperatures and/or different grainsizes, and, accordingly, the outermost surface of the molded product 3coming into contact with the surface of the die cavity 1 has theappearance of the mixed resin materials used. Consequently, theappearance of the product has a pepper and salt pattern which isproduced by the difference in the melting temperature, color, and grainsize between the resin materials to be mixed and in which some of thegrains clearly appear and others do not.

In FIG. 2, the heating device 4 is provided in the die 2 and ispreferably in the form of a sheathed heater. The sheathed heater can bereplaced with a pipe in which a heating medium flows. In thealternative, the pipe can be used as a cooling means for the moldingdie, by properly controlling the temperature of the heating medium.

As can be understood from the above discussion, according to the presentinvention, since two or more powder resin materials having differentcolours are mixed at a desired mixing ratio to make a single powdermixture and then the powder mixture is loaded in a molding die which ispreheated to heat and melt the powder mixture, the molded product has apepper and salt pattern on its outer surface, in accordance with amixing state and a mixing ratio, of the powder resin materials.Furthermore, according to the present invention, the pepper and saltpattern can be modified by changing the colour, the grain size, etc., ofthe powder materials. Accordingly, outer coverings having variouspatterns on the outer surfaces thereof can be easily manufactured by thepresent invention.

I claim:
 1. A process for manufacturing a molded outer covering,comprising mixing at least two powder resin materials having differentcolours at a desired mixing ratio to make a single powder mixture,loading the powder mixture in a preheated die, and removing an excess ofthe powder mixture from the die, and then heating the powder mixture inthe preheated molding die to melt the mixture, so that a molded outercovering which has a pepper and salt pattern with different colours onits outer surface is obtained.
 2. A process according to claim 1,wherein said powder resin materials are polyvinyl chloride.
 3. A processaccording to claim 1, wherein said powder resin materials are copolymersof polyvinyl chloride.
 4. A process according to claim 1, wherein one ofsaid powder resin materials is polyvinyl chloride and the othercopolymers of polyvinyl chloride.
 5. A process according to claim 1,wherein said powder resin materials have different melting temperatures.6. A process according to claim 4, wherein the melting temperatures ofsaid powder resin materials are 160° C. to 220° C.
 7. A processaccording to claim 1, wherein said powder resin materials are made ofgrains having different diameters.
 8. A process according to claim 6,wherein the diameters of the grains are 50 to 200 μ.